WESTON Performs Causeway Remediation and Coastal Restoration for the U.S. Army Corps of Engineers New England District

Stratford Army Engine Plant, Stratford, CT

Located within the Housatonic River Estuary, the 124-acre Stratford Army Engine Plant was closed under the Base Realignment and Closure program and earmarked for potential transfer to the Town of Stratford, Connecticut. A man-made causeway, which formerly allowed facility access by seaplane, extends 800 feet into the mudflats of the Housatonic River. Environmental investigations of the causeway materials indicated volatile organic compound contamination and the potential for erosion and deposition of contaminants in adjacent sensitive ecosystems. WESTON conducted a targeted excavation of contaminated soils, installed an innovative cover system to prevent erosion of and direct contact with underlying soils, and restored the property for reuse as public recreational space.

“WESTON provided valuable feedback through constructability reviews, offered time and budget saving recommendations with regard to operations and monitoring, and aggressively resolved quality control issues that had potential to extend project cost and schedule.”

    —Michelle Clemens, Engineering Manager, Army Corps of Engineers

WESTON Meets Site Challenges

Concerns over potential geophysical instability of the causeway prompted WESTON to implement a construction approach that minimized stress on the underlying materials while meeting an aggressive schedule.

Because of potential negative impacts of sedimentation on sensitive oyster beds adjacent to the project area, state regulations prohibited work below the high-tide mark between April and September. Restricted to a 6-month construction window during the winter months, WESTON successfully installed cover system components within the tidal zone. Potential geophysical instability required frequent monitoring of the causeway surface elevation for settlement. WESTON’s construction approach allowed work to continue without interruption, enabling the team to meet regulatory, environmental, and engineering requirements.

Working on a highly secure government facility, WESTON carefully planned and executed an aggressive schedule with no reportable lost days due to injury or accidents.

Site Challenges

• Performed abatement and demolition to improve future access to the causeway

• Performed work during nonstandard hours to accommodate a tidally influenced project area

• Completed construction on schedule despite low-tide windows as short as 2 hours

• Minimized potential impacts on sensitive ecological receptors

• Stabilized man-made causeway and installed protective cover system

Innovation and Value Engineering   

Operating under strict environmental regulations and engineering specifications, WESTON implemented a range of site-specific value-added solutions:

WESTON excavated contaminated soil for off-site disposal and demolished two asbestos-contaminated buildings to improve access to the causeway. WESTON graded and contoured the causeway surface and installed a dual-component engineered cover system to prevent direct contact between sensitive ecological receptors and the remaining underlying contaminated soil.

WESTON conducted a geotechnical analysis to determine maximum allowable point loads on the potentially unstable causeway surface. WESTON deployed smaller, more maneuverable equipment and reduced the size of individual cap components to avoid exceeding point load constraints and increase safety during construction.

The lower cover system consisted of rock-filled polymeric marine mattresses and was installed along the causeway within the tidal zone to stabilize contaminated materials and prevent erosion. The second component consisted of sand bedding and interlocking concrete blocks installed along the top surface of the causeway to stabilize underlying materials and prevent direct contact by human or ecological receptors. For both components, this project constituted an innovative application. WESTON worked closely with the design engineer and product manufacturers to meet stringent design tolerances and project-specific quality control requirements.

Project Stakeholders

WESTON communicated regularly with numerous project stakeholders, including the client representatives and regulatory agencies. Because restoration required two distinct design plans, WESTON encouraged partnering sessions to dovetail design plan implementation and resolve construction issues, therefore limiting delays, ensuring a high-quality product, and restoring an environmentally sensitive coastal area.

Future Goal: Reuse as a Town Park

• Innovative cap design ensured structural stability in an environmentally sensitive estuary

• WESTON partnered with critical stakeholders and maintained communication with local, state, and federal constituents to ensure a team-based approach and drive project completion

• WESTON completed work within an aggressive cold-weather schedule

• All project phases supported the ultimate goal for the site: The beneficial reuse of the causeway as a public park

• Incorporated Town of Stratford design elements into surface construction to provide subsurface utilities necessary for use